The present invention relates generally to cutting tools, and more particularly to cutting tools having a work piece feed mechanism operative to incrementally feed a work piece into the cutting tool.
Hand tools for cutting material are well-known. Such tools may be manually actuated or powered by a motor, compressed air, or the like. Conventional cutting tools being referred to generally include a pair of opposing jaws with one or two sharpened edges which pivot such that the jaws can be separated and brought together, often using levers to actuate the jaws, forcing the sharpened edge(s) against the material to be cut. The cutting stroke generally begins with the jaws being separated as the levers are moved apart. The material to be cut is inserted between the opened jaws and the jaws are forced together as the levers are moved together, creating a force which exceeds the strength of the material within the jaws, thus cutting the material. Typically, the jaws come together in either a shear action (e.g. scissors), where the jaw edges overlap at the end of the cutting stroke, or in an abutting action (e.g. typical bolt cutters), where the jaw edges abut one another at the end of the cutting stroke. The force imposed on the material for a given lever force increases as either the length of the levers (as measured from the point of application of force to the levers to the lever pivot point) increases or the distance between the pivot point and the work piece decreases.
A deficiency of the prior art is that conventional shear type cutting tools are not suitable for cutting relatively thick materials. When cutting very thin materials, shear type tools work well because the work piece can be entered and advanced successively with limited opening of the blades. However, as the thickness of the work piece increases, the cutting action becomes less efficient. With shear type cutting tools, twisting forces are developed by the non-aligned cutting members. As the thickness of the work piece increases, the twisting forces tend also to increase. Twisting forces are undesirable in that they tend to cause the blades to misalign (in turn tending to further increase the twisting forces), decreasing the cutting force applied to the work piece and potentially damaging the cutting edges.
Typically, cutting tools with abutting jaws, such as cutting pliers or bolt cutters, are used to cut relatively thicker objects such as wire cable, bolts and rods. The abutting, in-line cutting action of these tools, where the cutting forces are in alignment, eliminates or minimizes the twisting forces characteristic of the shear type devices. However, conventional abutting jaw type devices also suffer from some deficiencies. The jaws must be moved from their abutting closed position to an open position such that the jaws are spread sufficiently to accommodate the full thickness of the work piece, which typically requires substantial movement of the actuating levers. However, to maintain mechanical advantage, the cutting edge(s) must be close to the pivot(s) and the length of the edge(s) must be limited. Also, the angular spread of the jaws must be limited to limit the component of the forces that the jaws apply to the object which tend to push the object from the jaws. The limited jaw length, angular spread, and mechanical advantage that can be generated limit the thickness of the objects that can be cut by conventional hand tools with abutting jaws. Furthermore, at some point, the thickness of the object becomes so great that it is not possible to generate sufficient mechanical advantage to sever the object.
A need exists, therefore, for a cutting tool with jaws adapted to cut relatively thick, high strength materials, such as metal cables.